Distribution of enzyme-bearing cells in GM(2) gangliosidosis mice: regionally specific pattern of cellular infiltration following bone marrow transplantation

Tissue distribution of beta-hexosaminidase was investigated using 5-bromo-4 -chloro-3-indolyl N-acetyl beta-D-glucosaminide (X-Hex) as substrate in wil d-type mice, four GM, gangliosidosis model mice (Hexa-/-, Hexb-/-, Gm2a-/- and Hexa-/-Hexb-/-) and Hexb-/- mice that received bone marrow transplantat ion (BMT). In wild-type mice histochemical localization of beta-hexosaminid ase was detected in the perikarya of the majority of neurons, small process -bearing microglial cells, perivascular macrophages, and macrophages in the choroid plexus and leptomeninges. X-Hex positivity was also noted in the r enal tubular epithelium and macrophages in the liver and spleen. The staini ng pattern in the Gm2a-/- and Hexa-/- mice was generally similar to those o f wild type, but in these mice, X-Hex stain was also noted in some storage neurons with swollen perikarya. No X-Hex-positive cells were detected in He xb-/- or Hexa-/-Hexb-/- (DKO) mice. In Hexb-/- mice that received wild-type BMT (Hexb-/-+WBMT), many X-Hex-positive cells were detected in the spleen, and to a far lesser extent, in liver and kidney. In the CNS of these mice, X-Hex-positive cells were largely detected in the leptomeninges and choroi d plexus. Some positive cells were also detected, mostly in the perivascula r regions of the cerebrum, in particular in the regions of the posterior th alamus, brain stem and spinal cord. Some of X-Hex-positive cells were immun oreactive with Mac-1 and F4/80 antibodies and, thus, were cells of microgli a/macrophage lineage. X-Hex-positive staining was not detected in neurons i n these mice despite clinical improvement following BMT. This is the first time, as far as we know, that the regional distribution of the donor cells in the CNS has been investigated in a model of neuronal storage disease. Ou r study indicated that donor-derived cells of microglia/macrophage lineage infiltrated the CNS in a regionally specific manner following the BMT.